1. Field of the Invention
The invention relates to the delivery, selection and communication of information in an interactive format, and specifically to the delivery and selection of information delivered to a television user over a cable television system.
2. Description of the Related Art
Television has traditionally been a broadcast medium of entertainment. Service providers, such as television stations and networks, broadcast entertainment and information programming via a communications medium, such as a television network or cable system from the head-end of the communications system to a client or individual user at the receiving end of the system. While in the early days of television, this meant transmission of the broadcast signals through the air, more recently, cable networks have become commonplace. Transmission of the broadcast signals through the cable network provides a much wider signal transmission bandwidth and opens the possibility for the transmission of data in large quantities to the user. Bandwidth is defined as the information capacity of a particular transmission system. This traditional model of one-way communication between the service provider and the user has recently begun to change with the proliferation of interactive communication between the client and the service provider.
The television and cable network communication medium is a particularly advantageous way to transmit a great volume of information from the service providers to the end users, the viewers, and to provide an interactive mechanism for the viewer to utilize services such as video on demand, home shopping, interactive games, and home banking using the television as the interface. However, using television as the mechanism for correspondence between the service provider and the end user requires extensive modification of existing communication hardware to provide one or more of the following: greater signal bandwidth, more powerful head-end servers, and more powerful end-user receivers.
As shown in FIG. 1, a typical cable television system comprises four main elements: the head-end 10, a central originating point of all signals carried, where signals are received from service providers (television networks, special channels, etc.) in process; a trunk system 12, the main artery carrying signals through a community; a distribution system (including trunk bridging amplifiers 14), which is bridged from the trunk system and carries signals to individual neighborhoods for distribution to subscribers; and subscriber drops 16, including individual lines 18 to subscribers' television sets fed from taps (Area 1, Area 2 . . . Area X) in the distribution system. The head-end may include a satellite antenna system, tape processing, live programming cameras, signal-processing equipment, pilot carrier generators, combining networks, and equipment for bi-directional interactive services. The subscriber equipment may comprise end-user terminals, converters, de-scramblers, teletext decoding equipment, and the like, depending on the particular service in place and the sophistication in bandwidth of the given system. The trunk system may be physically composed of open air broadcasts, fiber optic lines, coaxial lines, or a combination of each.
In addition to providing video and music programming, in an interactive system, a significant quantity of information must be transmitted to the viewer as part of the interactive service environment. For example, the interactive environment may include several different interface screens utilizing a "multi-media" format (combining several different types of data, video, and audio), and a pointer or other means (such as a control pad-controlled cursor) for interacting with each of the data, audio, and video elements on the interface screen. As yet, no standard transmission or interaction format for the distribution system has been settled upon, and a number of standards are currently under development by television, telephone, or other communications providers.
A number of commercial services currently exist which provide broadcast programming along with data to a home viewer. Perhaps the most basic of these is commonly referred to as "Teletext," and provides cyclical digital data inserted in the vertical blanking interval of a video signal. (The vertical blanking interval is a standard interspersed period in a video signal which is approximately the black level of the signal, used to accommodate retrace periods of display scanning.) The amount of data which may be supported and transmitted by the Teletext system is limited by the bandwidth of the vertical blanking interval. As such, the data capacity is limited and the net result is usually the provision of this format of a few lines of text at the base of a television screen in the user's home. Teletext services can provide a viewer with a wide variety of useful information which can be program oriented, or completely independent of the program. The viewer uses a remote control key pad to select television images, teletext pages, or a combination of both. Some forms of two-way teletext exist, but these systems usually include an entry keyboard and a return link, via a telephone line, to a database.
A second commercial service to provide data over television transmissions is known as the "Sega Channel." The objective of the Sega Channel is to allow users of the Sega video game system to download software games directly from a broadcast channel for use on the game system rather than requiring the individual user to go to a retail store to purchase game cartridges. The Sega Channel broadcasts game program data on a standard cable channel via a cable network, in a continuous data stream of software games which the user may desire to download. Each game is broadcast at a different time, and broadcast information includes game identification information which is decoded by the game system in the user's home and which identifies the game to the system for downloading. The game system shows the individual user a selection menu on the user's television from which the user can select the particular game he or she wishes to download. When the game is transmitted over the broadcast medium at the appointed broadcast time, the game will be downloaded into the game system and the user may then play the game in the game unit. The Sega channel transmission scheme does not include any provision for "backchannel" information from the user to the information service provider.
Another commercial broadcast system which does provide some backchannel communication, but is limited to smaller broadcast environments, is commercially known as "Spectravision." Spectravision is generally set up in small environments such as hotels, resorts, or other limited areas, and the viewer is provided with one or more screens of information for video on demand, and hotel services such as in-room checkout, room service, and billing queries. The user, through an end-user box and accompanying remote control interface, can request in-room movies through the video on demand interface, request account information, or perform a check out, all through the Spectravision interface. Information which must be transmitted to the user in this system includes the complete video on demand menu (several screens of data), customer services menus and summaries of account information on the customer's charges during the stay in the hotel, and menus which the consumer may scroll through on demand and select to perform such services. This usually represents a fair amount of textual information, however, the backchannel communication for such a system is minimal, thereby limiting user response and choice. A local server for the particular small area which Spectravision services is all that is required. Spectravision also provides the viewer with the ability to switch between dedicated Spectravision services and regular full broadcast television services.
In providing interactive services in larger cable network applications, the main problem which arises is that of server and communications overhead. Allowing each subscriber to browse and navigate through all available services, (such as an electronic program guide for video-on-demand services,) creates substantial processing overhead on the head-end server. This, in turn, requires that the speed and capacity of the head-end server be increased for the system as a whole to be commercially effective, which increases the cost of the system.
As shown in FIG. 2, an interactive delivery system requires a physical delivery system which provides backchannel communication. An attempt to provide a fully interactive television interface on a larger scale will be made by U.S. West, Inc., a telecommunications company, which will conduct a trial of an interactive system in Omaha, Nebr. In the U.S. West example, the network configuration will comprise a broad-band network to provide video and data services. The broadband network is comprised of a head-end broadcasting server 20 providing transmission to a plurality of video switches 24 and nodes 26. The video switch will transmit packets of data continuously or in bursts through the broad-band network. The video switch 24 will deliver signals to a node 26 that will serve from 200 to 2,000 homes. From the video node, dual co-axial cables A,B will be used for distributing video signals to a pedestal that will contain video distribution equipment, video interaction equipment, and an optical network unit. As shown in FIG. 3B, the video portion of the network is a dual co-axial cable design, with a sub-split design "A" cable providing 650 mhz of bandwidth to support 77 analog channels, up to 136 digital channels, and 25 mhz of shared upstream (or backchannel) capacity. The spectrum "B" cable provides 500 mhz of bandwidth to support up to 664 digital channels and 107 mhz of shared backchannel capacity. The split design allows for channel frequency compatibility of the analog channels with existing cable-ready TV sets, while the "B" channel provides backchannel capacity anticipated for the more interactive services expected to use digital channels. A spectrum of the transmission bandwidth of approximately 1 GHz is shown in FIG. 3A. This U.S. West embodiment illustrates how the aforementioned problems will result. The communications overhead on the head-end which will result from backchannel communications and viewer demand, even in the limited service area of the experiment, is quite significant.
When a user is browsing or merely viewing the possible selections available from the head-end, communication with the head-end server is required; however, no revenue for the service provider is created during the browsing events. Thus, activities such as browsing increase the cost for all revenue-generating activity. It would therefore be desirable to reduce the load on the head-end server which is required for any such non-revenue generating activity.
In the aforementioned prior art transmission schemes, the bandwidth allocated from the head-end to the home user is quite large in comparison to the backchannel band-width allocated for viewer communication to the server. Because the total amount of bandwidth through the backchannel which will be required at the head-end at any given time will fluctuate with the use pattern of the subscribers (the number of subscribers making demands on the head end at a given time and the activities of those subscribers), such fluctuation will place unpredictable communication latencies on the system. It is important to determine all communication latencies on the backchannel to determine operating parameters for a commercially viable system and for service providers to configure their programming so that the user is not unduly burdened during the periods of maximum latency in the system.
Additional processing overhead is required during handshaking. Handshaking comprises the interaction with all communications to the server involving a response mechanism to the user which ensures reliable communications between the server and the user. A simplified communications model that does not require, or at least minimize, server intervention in handshaking is desirable.
Congestion within the communications pipeline resulting from large bursts of backchannel communication can impair the quality of service to viewers by resulting in a large latency period. A large volume of backchannel communication or a "connection storm" can occur when large numbers of viewers simultaneously request service, as at the start or end of a popular event, or after a power outage when the users are attempting to re-establish service. This again can result in unpredictable latency times.
Each server has a finite bandwidth, and congestion will occur at the server as the number of requests it must handle increases. Indeed, in large scale implementations, a network of servers will be required to distribute requests and balance the load on the network infrastructure, also increasing the expense of providing service to users.
Any one or more of the aforementioned difficulties could result in the interactive viewing experience being less seamless than the viewer currently experiences with analog television signals. For any system which utilizes digital communication technology to transmit data to a viewer to be commercially viable, the system must make the viewing experience appear as seamless as the viewer's current viewing experience. Viewers have come to expect a minimum level of broadcast quality in television viewing, thereby requiring any new system be comparable to current systems in the manner in which programming and information is presented to the viewer.
Thus, it is desirable to provide an interactive system which will overcome the aforesaid deficiencies in a broadcast communications medium.
One means of disseminating a large amount of data over a network and is the "Data Cycle" proposal and research set forth by Bellcore (Bell Communications Research, Inc.). The data cycle is a proposal for a distributed, shared memory database implemented through use of a storage pump which continuously broadcasts the entire contents of the database over a ring network to a series of access managers which control, for example, SQL-type application access to the data which is broadcast on the network. In the embodiments described in a paper entitled "The Datacycle Architecture: A Database Broadcast System", authors Bowen, et al., a data rate of 52 megabytes per second is supported such that a 32 megabyte database stored on a single storage pump is entirely broadcast every 0.6 seconds. A user seeking to extract data from the database initiates a query through an access manager via one of any suitable number of applications. The access manager then extracts the data and provides it to the application and ultimately the user. The database is continually broadcast over the broadcast channel at a repeating rate, and therefore may be updated via an update manager coupled to the access managers and the storage pump.
As described in the Bowen, et al. paper, the system is useful, for example, in providing a directory assistance database which may be continually updated and provided to the directory assistance operators of a given telephone network.
In consideration of the aforesaid problems, a communications system which reduces the overall overhead at the head-end and still provides complete interactivity and a large quantity of information to the user is therefore desirable.